An enzyme found in the roots of soybeans could be the key to cars that run on air.

Vanadium nitrogenase, an enzyme that normally produces ammonia from nitrogen gas, can also convert carbon monoxide (CO), a common industrial byproduct, into propane, the blue-flamed gas found on stoves across America.

While scientists caution the research is still at an early stage, they say that this study could eventually lead to new, environmentally friendly ways to produce fuel —and eventually gasoline — from thin air.

"This organism is a very common soil bacteria that is very well understood and has been studied for a long time," said Markus Ribbe, a scientist at the University of California, Irvine, and a co-author of the new paper that appears in the journal Science.

"But while we were studying it, we realized that the enzyme has some unusual behavior," he added.

The organism that the researchers studied wasAzotobacter vinelandii, an economically important bacteria. A. vinelandii is usually found in the soil around the roots of nitrogen-fixing plants like soybeans.

Farmers like plants that containA. vinelandii because the bacteria use a suite of enzymes to turn unusable atmospheric nitrogen into vital ammonia and other chemicals. Other plants can then take up those chemicals and use them to grow.

Ribbe and his co-authors isolated one particular enzyme, vanadium nitrogenase, to convert nitrogen into ammonia. Then the California scientists removed the nitrogen and oxygen the enzyme is used to and filled the remaining space with CO.

Without oxygen and nitrogen, the enzyme began to to turn the CO into short chains of carbon two and three atoms long. A three-carbon chain is more commonly referred to as propane, the blue-flamed gas used in kitchens across America.

Scientifically, the new function of vanadium nitrogenase is a "profound discovery," said Jonas Peters, a scientist at Cal Tech who said he nearly leapt from his chair when the results were announced at a recent conference.

The new research could have some very important industrial applications, Peters said.

"Obviously this could lead to new ways to create synthetic liquid fuels if we can make longer carbon-carbon chains," said Ribbe.

The new enzyme can only make two and three carbon chains, not the longer strands that make up liquid gasoline. However, Ribbe thinks he can modify the enzyme so it could produce gasoline.

If perfected, the technique could lead to cars partially powered on their own fumes. Even further into the future, vehicles could even draw fuel from the air itself.

That perfection won't happen anytime soon, say both Ribbe and Peters.

"It's very, very difficult," to extract the vanadium nitrogenase, said Ribbe.

Scientists have known about this enzyme for a long time because of its importance in agriculture. They even isolated the genes that encode for vanadium nitrogenase more than 20 years ago, which opens the door to genetic engineers and synthetic biologists.

But the technology to extract, grow and store large quantities of the enzyme has only developed within the last few years, which made this new research possible.

Further advances will be necessary before air and bacteria cars rule the road.